Electric heater



July 25, 1939;. c. SYKES ET m. 2,167,494

ELECTRIC HEATER Filed Feb. 16, 1937 u i 1 a. a i m lmventowi Charfies Sgi'ies, William Needham, b ?/JMZZW4 Their" AtLOPWQH.

Paie'nted'July :5, 193a" 2,167,494

UNITED sTATEs PATE-NT orrlc -z clmloo Sykes, Needham, Sale, England, alignors to General Electrio Company, a corporation of New York Application rooms- 16, 1937, Serial No. 126,044

' Great Britain February 28, 1938 3 Claims- (Cl. 201-67) This invention relatesto electric heater ele- A resistor member I is mounted within the ments of the kind in which the resistor wire or sheath. A metallic terminal tube'l surrounds the strip is enclosed'in a sheath and insulated there end portion of the resistor 3 and projects downfrom by a metallic-oxide packing which is formed 9 wardly beyond the mouth of the sheath to pro- 5 by treatment of the metal or a salt of the metal vide'a connection for a-supply lead 5; This may I when in position in the sheath. I be effected as in the manner shown by pinching The invention has particular reference to the together the sides of the tube 4 around the lead provision of terminals for such heater elements. 5 as indicated at 8, the end of the resistor 3 being The object ofthe invention is to produce an of course held within the pinched portion 6 so as lll'improve'd heater element in which the resistor to make electrical connection; the sides of the 1. and metallic oxidepacking are protected ag iiist tube end are welded or soldered together. A corrosion and deterioration, more particularly spacing tube I of silica or other suitable matedue to moisture, and which is of a strong and rial is interposed between the resistor I and rigid'constructiom. the terminal tube 4, whilst a collar I of steatitc According to the present invention, a short or. other heat resisting material surrounds the lelength of metallic tubing is inserted within the sistance adjacent the end'*-of the metallic tube 4 sheath of the heater to constitute a terminal'for and serves primarily as an electrical insulator, ,the resistance member, in such a manner that this being de ir le On account of the e tial the tubing surrounds the end portion of the -rediiference that will exist between the resistor N sistance or a lead secured thereto, and filling 'at this point and the metallic tubing owing to the n the sheathing with a"suitable espansively oxfact that it is theextreme end portion of the ldizable metal, such as magnesium, or a salt resistor which is connected -to the tubing I. thereof, so as to surround the resistance and the. Metallic oxide packing 9 surrounds the resistor terminal tube along a portion of its length and 3 and the upp r part of the terminal tube 4. This as then treating the metal to form the metallic oxide packing is preferably obtained by filling the is packing, the terminal being located substantialsheath with metallic magnesium and then pass- 1y centrally in the sheathrduring the packing ing-steam through the sheath to convert the meprooess, and finally sealing'the end of the sheath tallic magnesium to magnesium oxide. Sand I. in a moisture-proof manner and insertinga bush-v yb a d around the celled P 1 the 30 ing of refractory material'to protect the sealing resistor 3. 1

,material,, 1 The end of the sheath 2 is sealedbya bead The invention alsocomprlses an electric H of vitreous material which is-fused or sintered heater element of the kind referred to in which 'in position by h Such ma ri l may be 818-88 the end of the resistor wire is surrounded by a or lead borate, but is preferably a mixture come f 86 short length of metallic tubing constituting a prising one part of lead borate and two parts of 8 terminal andspaced from the sheath, the resistairconium cement. -The latter material consists ance' memberand also the terminal tube for a. of silicate with a bonding material p rtion orits l ngth being surrounded bya mag such as ball clay. Asmh wn n the drawing. th nesium oxide packing, whilst the ehd of the bore of the sheath maybe enlarged for the ac'-' 40 sheath is provided with lamp of reiractory matecommodation of the sealing material. A cap i2 49 rial through which the passes, and sealinserted in the mouth of the sheath 2 protects ing material is interposed between th magnethe sealing. material against external damage, slum oxide packing and the refractory ca and this cap is preferably held in position bythe For amore complete understanding of in- 'iiattened portion I or the terminal tube. In'some 43 vention,' reference should be had totheaceomcases the terminal tube may be made relatively 4| panying drawing in which the single figure is a long so that the end portion of the sheath does sectional view' r the end portion oia heater elenot become heated to the extent which it would K ment and the-structure therefor arranged in aeii the coiled portion of th resistor extended to cordance with this invention. theend oi the sheath.

l0 In the drawing, I a terminal box In making the heater element, the resistor I so which supports the heater element, which terisilrst inserted in the sheath and then the colminal boxmay be suitably hinged or pivoted to a lar I placed around it and the tube 4 stove framework to permit of the removal of the and spacer I. 'lhe metallic magnesium or other heater element.- A sheath 2 of the heater elemetal or metallic saltis inserted in the sheath ll ment passes through the side of the terminal box; so as to surround the'resistor, element and a of the sheath, and the end portion [of the tersin , the inner end of the tube, filling the sheath with minal tube is pressed flat around the end of the resistor and the lead 5 and is sealed by soldering or welding,

While we have shown a. particular embodiment of our invention, it will be understood, of course, that we do not wish to be limited thereto since many modifications may be made. and we, there-' fore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention,

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of making a heater element of the kind having a helical resistor member 10- cated within a sheath and insulated therefrom by a metallic oxidewhich comprises forming a resistance conductor into a helical coil having a straight terminal end portion, inserting said coil in a sheath with said end portion in the end of said sheath, inserting a metallic tube constituting a terminal for said resistor member within the sheath so as to surround the straight end portion of said resistance, connecting the straight end portionof said resistance to the outer end of said metallic tube, inserting an electrically insulating sleeve in the sheath between the turns of the helical coil and the inner end ofsaid tube to prevent the turns from accidentally engaging a, metal that expands when oxidized so as to surround said resistor, said insulating sleeve and also the terminal tube along a part of its length,

then treating said metal to form the metallic oxide that packs the sheath, said insulating sleeve and terminal tube being located substantially portion, a sheath enclosing said resistor member a and insulated therefrom by electrically insulating material, the said end portion of the resistor member being surrounded by a length of metallic tubing constituting a terminal and spaced from the sheath, means connecting the outer end of said straight end portion with the outer end of said metallic tubing, an electrically insulating sleeve interposed between the turns of said helical resistance and the inner end of said tubing surrounding the straight end portion of said resistor member so as to prevent'the turns of said resistor member from contacting the adjacent end of said metallic tubing, said insulating material surrounding the resistance member and also the terminal tube for a portion of its length, and holding said insulating sleeve between said turns and said tubing.

3. An electric heating element comprising a resistor member, a sheath enclosing-said resistor member and insulated therefrom by electrically insulating material, theend of the resistor memher being surrounded by a length of metallic tubing constituting a terminal and spaced from the sheath, a tube formed of an electrically insulating material within the terminal tube separating the tube from the portion of the resistor member received in it and centering said portion of the resistor member in the tube, said insulating material surrounding the resistance member and tween the insulating material and the refractory OED.

CHARLES SYKES. WILLIAM NEEDHAM. 

